This invention relates to a conveyor, and more particularly, to a roller conveyor for a tire uniformity measurement machine.
A tire uniformity measurement machine has an upper rim and a vertically-movable lower rim adapted to engage and lift a tire up to the upper rim where it is held and inflated. A load wheel is movable into engagement with the inflated tire the tire is rotated at a predetermined speed, during which forces indicative of lack of uniformity are measured. Tires must be conveyed into the machine, stopped, centered prior to engagement by the lower rim and thereafter conveyed out of the machine.
In machines that existed prior to the present invention, the conveyor has entrance and exit rollers with a space between them of sufficient dimension to permit the passage of the largest lower rim to be employed in the machine. In that gap are diametrically-opposed sets of three partial rollers, the ends of the partial rollers, when spread apart, defining the largest opening between which the largest lower rim will pass. Each tire having a different size of bead defining its opening will have a mating set of rims adapted to be mounted in the machine. Therefore, the conveyor must be able to accommodate various diameters of tire rims. The rollers are mounted on carriages which are movable toward and away from each other to vary the size of the opening so as to provide the smallest possible opening adapted to permit the passage of the smallest rim and the largest opening for passage of the largest rim.
All but the center roller are driven by a sprocket and chain system. The three partial rollers are mounted on short shafts and are keyed to the shafts so as to be movable in an axial direction. The rollers, that are mounted on and driven by the shafts, have ends fixed to a transversely slidable carriage on each side of the machine. The center roller is not driven because it is not long enough to be supported on a driving shaft.
The conveyor thus described presents a problem. It does not always reliably convey a tire out of the machine after the measurement process has been performed. The tire tends to tilt as it starts its movement out of the opening through which the tire rim has passed and thus has to be driven "uphill" with the possibility of hanging up on the ends of the partial rollers.